Any human or animal is under not a few stresses, and these stresses exert great effects not only on the nervous system, but also on the immune system via the nervous system. In general, under stress-loaded states, a hormone such as a glucocorticoid or the like which is secreted from the adrenal gland is secreted as an antistress hormone to direct an action to heighten vigor and the like. However, on the other hand, it has been known that the glucocorticoid reduces the growth ability or the function of immunocompetent cells and also acts disadvantageously on the living body by inducing apoptosis of the immunocompetent cells, accelerating degradation of proteins, inhibiting their synthesis, and the like (see for example, non-patent literature 1 and non-patent literature 2). Therefore, if the stress states persist and become chronic, the glucocorticoid is secreted continuously to induce a variety of symptoms caused by the action of glucocorticoids, which is disadvantageous to the living body, for example, the so-called secondary problematic symptoms due to chronic stress(es), such as decrease in infection-defense ability, delay of wound healing, metabolic disorders, and the like.
Against the stress(es), drugs such as antianxiety drugs, sleeping drugs, and the like are considered to be an effective means alleviating temporarily the reaction of body and mind when exposed to the stress(es). However, there has not been known any antistress drugs that are free from side effects and can be taken habitually and continuously. For example, although a benzodiazepine drug which is a representative antianxiety drug, is said to alleviate anxiety, tension, depression and muscle tonus without affecting the level of consciousness, it has been known that a high-dose administration or a repetitive administration of the drug causes abstinence symptoms, such as convulsion, delirium, and the like, as well as side effects, such as sleepiness, stagger, dizziness, hepatopathy, leucopenia, and the like. Also, a variety of tablets or drinks are commercially available as an object of an analeptic or a refresher of the body, but any effect against the stress(es) is/are not distinct at present.
On the other hand, a composition which comprises as an active ingredient a saccharide containing 3-O-α-D-glucopyranosyl-D-glucose as a structural unit has been known to have the actions of immunostimulants (patent literature 1), NK cell activators (patent literature 2), QOL improvers (patent literature 3), foods or beverages to suppress reduction in the immune function due to nutritional disorders (patent literature 4), and the like. However, these literatures do not describe at all that the above-mentioned saccharide has an antistress action, and improve or suppress symptoms associated with reduction in function of immunocompetent cells or apoptosis of the immunocompetent cells occurring under the influence of the glucocorticoids especially due to chronic stress(es), and the like. As stated above, although the above-mentioned saccharides have been known to stimulate the immune system, it has not been known at all how the saccharide acts against the stress(es), especially against a variety of symptoms associated with chronic stress(es).
Patent literature 1: Japanese Patent No. 3396129
Patent literature 2: Japanese Patent Application Laid-Open No. 2002-265366
Patent literature 3: Japanese Patent Application Laid-Open No. 2002-265385
Patent literature 4: Japanese Patent Application Laid-Open No. 2002-325555
Non-patent literature 1: Tomio Tada, “Immunology Illustrated,” p 178, Nankodo, 2000
Non-patent literature 2: Katsuiku Hirokawa, “Cross Talk on Nerve, Internal Secretion and Immunity,” p 177-185, Japan Scientific Societies Press, 1993